1 files changed, 73 insertions, 0 deletions
diff --git a/library/std/src/sys/wasi/io.rs b/library/std/src/sys/wasi/io.rs
new file mode 100644
index 000000000..ee017d13a
--- /dev/null
+++ b/library/std/src/sys/wasi/io.rs
@@ -0,0 +1,73 @@
+#![deny(unsafe_op_in_unsafe_fn)]
+
+use crate::marker::PhantomData;
+use crate::slice;
+
+#[derive(Copy, Clone)]
+#[repr(transparent)]
+pub struct IoSlice<'a> {
+    vec: wasi::Ciovec,
+    _p: PhantomData<&'a [u8]>,
+}
+
+impl<'a> IoSlice<'a> {
+    #[inline]
+    pub fn new(buf: &'a [u8]) -> IoSlice<'a> {
+        IoSlice { vec: wasi::Ciovec { buf: buf.as_ptr(), buf_len: buf.len() }, _p: PhantomData }
+    }
+
+    #[inline]
+    pub fn advance(&mut self, n: usize) {
+        if self.vec.buf_len < n {
+            panic!("advancing IoSlice beyond its length");
+        }
+
+        unsafe {
+            self.vec.buf_len -= n;
+            self.vec.buf = self.vec.buf.add(n);
+        }
+    }
+
+    #[inline]
+    pub fn as_slice(&self) -> &[u8] {
+        unsafe { slice::from_raw_parts(self.vec.buf as *const u8, self.vec.buf_len) }
+    }
+}
+
+#[repr(transparent)]
+pub struct IoSliceMut<'a> {
+    vec: wasi::Iovec,
+    _p: PhantomData<&'a mut [u8]>,
+}
+
+impl<'a> IoSliceMut<'a> {
+    #[inline]
+    pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> {
+        IoSliceMut {
+            vec: wasi::Iovec { buf: buf.as_mut_ptr(), buf_len: buf.len() },
+            _p: PhantomData,
+        }
+    }
+
+    #[inline]
+    pub fn advance(&mut self, n: usize) {
+        if self.vec.buf_len < n {
+            panic!("advancing IoSlice beyond its length");
+        }
+
+        unsafe {
+            self.vec.buf_len -= n;
+            self.vec.buf = self.vec.buf.add(n);
+        }
+    }
+
+    #[inline]
+    pub fn as_slice(&self) -> &[u8] {
+        unsafe { slice::from_raw_parts(self.vec.buf as *const u8, self.vec.buf_len) }
+    }
+
+    #[inline]
+    pub fn as_mut_slice(&mut self) -> &mut [u8] {
+        unsafe { slice::from_raw_parts_mut(self.vec.buf as *mut u8, self.vec.buf_len) }
+    }
+}